• Journal of Information Technology Applications and Management
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• v.22 no.3
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• pp.105-114
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• 2015

This paper presents a fast Time Difference of Arrival (TDOA) estimation for sound source localization. TDOA is the time difference between the arrival times of a signal at two sensors. We propose a partial cross correlation method to increase the speed of TDOA estimation for sound source localization. We do this by predicting which part of the cross correlation function contains the required TDOA value with the help of the signal energies, and then we compute the cross correlation function in that direction only. Experiments show approximately 50% reduction in the cross correlation computation time thereby increasing the speed of TDOA computation. This makes it very relevant for real world surveillance.

• Journal of Environmental Science International
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• v.14 no.6
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• pp.543-553
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• 2005

In recent days, photochemical smog due to the rapid industry development and vehicle increasement has become a critical pollutant in the metropolitan area and the number of ozone alarm signal has increased every year. This research was performed to evaluate VOCs emission source characteristics and concentration of VOCs in Daegu. The site average concentration was observed in the following order: industrial area > commercial area > residential area. Most of the VOCs species except toluene showed variations with higher concentration during nighttime, and lower concentration during the daytime. The major VOCs of stationary emission source were BTEX(benzene, toluene, ethylbenzene. xylene) and methylene chloride, trichloroethene and styrene. Also, those of automobile exhaust were toluene and benzene. Also, the major VOCs concentration emited by the vehicle fuel was observed in the following order: gasoline > light oil > liquefied petroleum gas (L.P.G). Correlation coefficients values were estimated between major VOCs such as toluene, ethylbenzene, m,p-xylene, o-xylene. Results showed that correlation coefficient values were significant magnitude above 0.76. Also, there showed highly significant correlations among ethyl benzene, m,p-xylene, and o-xylene concentration(Pearson correlation coefficients, r=0.868-0.982). Calculated correlation coefficients among commercial area,industrial area and residential area were 0.934-0.981, they showed high correlation. There showed highly correlation between stationary emission source and industrial area, compared with commercial area and residential area. Also, calculated correlation coefficients among commercial area, industrial area, residential area and automobile exhaust were 0.732, 0.725, 0.777, respectively.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.86-92
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• 2001

Various array processing techniques to identify the noise source position or bearing have been developed. Typical array processing techniques which are based on time delay between received signals at two sensors, are classified as conventional beamforming, correlation function and NAH (Near-Field Acoustic Holography) techniques which have their own characteristics with respect to application field and signal processing method. In this study, correlation function technique which could be applied for broadband noise source detection, is adopted and the effective detection technique is proposed considering the effects of source bandwidth and measurement noise correlation of noise sources. The validity of the Proposed technique is evaluated using the 3-dimensional nonlinear any which does not give 3-dimensional Position or bearing ambiguity

• Geophysics and Geophysical Exploration
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• v.15 no.3
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• pp.129-135
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• 2012

The simultaneous-source full waveform inversion improves the applicability of full waveform inversion by reducing the computational cost. Since this technique adopts simultaneous multi-source for forward modeling, unwanted events remain in the residual seismograms when the receiver geometry of field acquisition is different from that of numerical modeling. As a result, these events impede the convergence of the full waveform inversion. In particular, the streamer-type data with limited offsets is the most difficult data to apply the simultaneous-source technique. To overcome this problem, the global-correlation-based objective function was suggested and it was successfully applied to the simultaneous-source full waveform inversion in time domain. However, this method distorts residual wavefields due to the modified objective function and has a negative influence on the inversion result. In addition, this method has not been applied to the frequency-domain simultaneous-source full waveform inversion. In this paper, we apply a timedamping function to the observed and modeled data, which are used to compute global correlation, to minimize the distortion of residual wavefields. Since the damped wavefields optimize the performance of the global correlation, it mitigates the distortion of the residual wavefields and improves the inversion result. Our algorithm incorporates the globalcorrelation-based full waveform inversion into the frequency domain by back-propagating the time-domain residual wavefields in the frequency domain. Through the numerical examples using the streamer-type data, we show that our inversion algorithm better describes the velocity structure than the conventional global correlation approach does.

• Journal of Information Technology Applications and Management
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• v.24 no.1
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• pp.157-167
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• 2017

This paper proposes a simple sound source localization (SSL) method based on signal energies comparison and partial cross correlation for TDOA computation. Many sound source localization methods include multiple TDOA computations in order to eliminate front-back confusion. Multiple TDOA computations however increase the methods' computation times which need to be as minimal as possible for real-time applications. Our aim in this paper is to achieve the same results of localization using fewer computations. Using three microphones, we first compare signal energies to predict which quadrant the sound source is in, and then we use partial cross correlation to estimate the TDOA value before computing the azimuth value. Also, we apply a threshold value to reinforce our prediction method. Our experimental results show that the proposed method has less computation time; spending approximately 30% less time than previous three microphone methods.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.781-784
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• 1994

Detecting partial discharge(PD) and locating its source are one of many diagnosis methods. Location the PD source is very important to reduce the time and cost of repairing power transformers. And to locate the PD source, the cross-correlation method is a well known one. But there many spurious peaks in cross-correlation, and occasionally, some peaks could be bigger than the true one. In order to analysis these spurious peaks and to reduce them, we have done many experiments and simulations. As the results we could reduce the spurious peaks, and get well defined cross-correlation from which it is easy to locate the PD source accurately.

• Journal of Astronomy and Space Sciences
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• v.29 no.3
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• pp.253-258
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• 2012

We revisit the relation between the peak luminosity $L_{iso}$ and the spectral time lag in the source frame. Since gamma-ray bursts (GRBs) are generally thought to be beamed, it is natural to expect that the collimation-corrected peak luminosity may well correlate with the spectral time lag in the source frame if the lag-luminosity relation in the GRB source frame exists. With 12 long GRBs detected by the Swift satellite, whose redshift and spectral lags in the source frame are known, we computed $L_{0,H}$ and $L_{0,W}$ using bulk Lorentz factors ${\Gamma}_{0,H}$ and ${\Gamma}_{0,W}$ archived in the published literature, where the subscripts H and W represent homogeneous and wind-like circumburst environments, respectively. We have confirmed that the isotropic peak luminosity correlates with the spectral time lag in the source frame. We have also confirmed that there is an anti-correlation between the source-frame spectral lag and the peak energy, $E_{peak}$ (1 + z) in the source frame. We have found that the collimation-corrected luminosity correlates in a similar way with the spectral lag, except that the correlations are somewhat less tight. The correlation in the wind density profile seems to agree with the isotropic peak luminosity case better than in the homogeneous case. Finally we conclude by briefly discussing its implications.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.8
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• pp.664-671
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• 2006

We propose the correlation to predict the spreading thermal resistance on a plate with symmetrical four heat sources. The correlation transforms four heat sources to a single equivalent heat source and then the spreading thermal resistance can be obtained with the existing equation for a single heat source. When the four heat sources are mounted on a square base plate, the correlation is expressed as a function of the heat source size, the length of base plate, the plate thermal conductivity and the distance between heat sources. Compared to the results of three-dimensional numerical analysis, the spreading thermal resistance by the proposed correlation is in good agreement within 10 percent accuracy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.379-386
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• 1992

In this paper a direction finding method which can which can estimate the direction angles of source signals impinging on the sensor array in which sensor noises are correlated is studied. This method performs the estimation of source direction angles form sensors, regardless of sensor noise correlation, by eliminating the sensor noise correlation coefficient which can be accurately estimated. Finally, this paper shows, through the computer simulation, that the proposed, method is extremely useful and superior when there exists the noise correlation between sensors, .

• Journal of KSNVE
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• v.7 no.2
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• pp.255-260
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• 1997

This paper describes 3-dimensional volume array of 4 microphones including a reference microphone which is capable of imaging wideband noise source position in 2-dimensional image plane. The cross correlation function and corresponding imaging function between a reference microphone and other microphone, are derived as a function of noise source position. The magnitude of the imaging function gives noise source mapping in image plane. Since the image plane is selective from a rectangular and a cylindrical plane, noise source position information such as range and bearing relative to the array is identified very much easily. Simulation results for typical source configurations confirms the applicability of the proposed array in noise control field.